Sychronize many asynchronous Ajax.Request

[maalek]

Hello

I have problem. When my page is load I build many objects (aprox 15)
by Ajax.Request (asynchronous : true) but last object I can create
when all previous object is ready. Any idea how do that ?

maaalek

[Alex McAuley]

Ask it to check a variable that is set as ready by all the others .. or make
it defer and be synchronous ..


Alex Mcauley
http://www.thevacancymarket.com

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[maalek]

Synchronous is simple way but object create time increses x3. How
function use to wait until all object is ready ? setInterval ?

maaalek

On 21 Lis, 14:32, "Alex McAuley" <webmas...@thecarmarketplace.com>
wrote:

> Ask it to check a variable that is set as ready by all the others .. or make
> it defer and be synchronous ..
>

> Alex Mcauleyhttp://www.thevacancymarket.com

[Alex McAuley]

You need to set variables in the objects/ requests and check them



Alex Mcauley

[T.J. Crowder]

Hi,

> Synchronous is simple way but object create time increses x3. How
> function use to wait until all object is ready ? setInterval ?

Probably setTimeout, but yeah; or setTimeout's Prototype wrappers
Function#defer / Function#delay. Have the code in question check its
preconditions, and if they're not met, setTimeout/defer/delay itself.
--
T.J. Crowder
Independent Software Consultant
tj / crowder software / com
www.crowdersoftware.com

[Eric]

Hi,

I'd launch all Ajax.Request except the last one with a onSuccess
handler that:
- set a flag
- if all flags are set, launch the last Ajax.Request

This way, you don't have to use timer, or loop calling yourself
recursively.

Eric

NB: I didn't test it, but you may increment a counter instead of using
many flags

[Alex McAuley]

The main problem is that due to the "ansynchronous" and the wait times /
serverside processing times ... you never know which will finish first nd if
the last request relies on the first one completing then its going to hard
fail !!...

Each one needs to set a variable to say its complete !



Alex Mcauley

http://www.thevacancymarket.com
----- Original Message -----
From: "Eric" <lefa...@gmail.com>
To: "Prototype & script.aculo.us" <prototype-s...@googlegroups.com>

Sent: Monday, November 23, 2009 2:30 PM
Subject: [Proto-Scripty] Re: Sychronize many asynchronous Ajax.Request

[david]

Hi all,

if you need to save all returned value, just save each request result
in an array.
Check the length of the result list to know when all request are
finished.

But we still turn around the same idea.
--
david

On 23 nov, 15:59, "Alex McAuley" <webmas...@thecarmarketplace.com>
wrote:

> The main problem is that due to the "ansynchronous" and the wait times /
> serverside processing times ... you never know which will finish first nd if
> the last request relies on the first one completing then its going to hard
> fail !!...
>
> Each one needs to set a variable to say its complete !
>

[Alex McAuley]

It would polute the variable and seriously eat RAM to save every result
response in an array, i would highly recommend staying away from it..

Alex Mcauley

[david]

I'm sorry Alex, but I definitely not agree with you !
First because there is existing method to cache the Ajax request and
they use local object to save the result (we have now some new way to
save locally a variable but it's not cross-browser).

And next, because an array is much more flexible than variables. you
could access each element independantly and have the length method (In
our exemple, to know how much elements have been saved). And if each
request should have a specific position in the array, length is no
more working, but Prototype have sugaristic method that help you
playing with Array the way you need.

But there is I think plenty way to do this.

--
david


On 23 nov, 23:44, "Alex McAuley" <webmas...@thecarmarketplace.com>
wrote:

> It would polute the variable and seriously eat RAM to save every result
> response in an array, i would highly recommend staying away from it..
>

[Alex McAuley]

Arrays are stored in memory, they are not a cookie so they do not get stored
on the client machine .. (and you yourself say that even if it was its not
cross browser)

To test .. Do 100 requests with large responses and save them all into an
array and see how much memory the web browser is eating each time you do
one...

In fact the actal request stays in memory unless you null the object - i
wrote a post on this in TJ's proto scripty wiki which has test cases to
prove it.

I dont see any reason ever to save the response of multiple requests in an
object that is saved in memory of the client's browser .... what happens if
they are on an iPhone or somehting with not alot of memory ?


Alex Mcauley

> http://groups.google.com/group/prototype-scriptaculous?hl=en.
>
>
>

[david]

Yes your right Alex, but the case of maalek did not mention such
numbers of request.
I think in his case using one array is better than using a lot (~14
differents variables).

btw, I'm interrest in "In fact the actal request stays in memory
unless you null the object" and after reflexion, that is logical, but
is it normal ??

--
david

On 24 nov, 09:37, "Alex McAuley" <webmas...@thecarmarketplace.com>
wrote:

> Arrays are stored in memory, they are not a cookie so they do not get stored
> on the client machine .. (and  you yourself say that even if it was its not
> cross browser)
>
> To test .. Do 100 requests with large responses and save them all into an
> array and see how much memory the web browser is eating each time you do
> one...
>
> In fact the actal request stays in memory unless you null the object - i
> wrote a post on this in TJ's proto scripty wiki which has test cases to
> prove  it.
>
> I dont see any reason ever to save the response of multiple requests in an
> object that is saved in memory of the client's browser .... what happens if
> they are on an iPhone or somehting with not alot of memory ?
>

[Alex McAuley]

Yes...

Objects and thier properties are built and stored in memory (how else would
they get built) - the CPU does the calculations and outputs the opcode to
the browser (which reads from memory) what it needs to do with the object
(In very simple terms)... So it stands to reason that if you dont remove the
Object from memory it will just add to the memory bracket.

To test...

Build a test page with a periodical ajax request and (on winblows) watch the
RAM that for instance firefox uses in the task manager go up and up and up.

Then close the whole browser (so it starts clean again) and assign the
periodical updater to a variable

var request=new Ajax.Periodical...({});

request=null;

And watch the difference between what happend in the first test and the
second...

In the second test the browser frees up 60-80% of the memory that it used to
make/process the request by nulling the object back to a null byte

If you look on TJ's proto scripty wikidot my results are there and the code
that accompanies it.

I assumed it was common knowledge that people garbage collected ajax
requests... Its not just prototypejs but every ajax style library that does
not garbage collect these requests


Alex Mcauley

[Matt Foster]

I'd recommend taking a look at my Ajax Service Queue approach, such
that all requests go through the service object, and in the subclass
for the queue's case won't send the next request until its predecessor
has returned. It needs to be updated for 1.6 but the idea is on the
wall for you to look at...

Most pertinently is the "onFinish" event which would work perfectly
for your circumstance.

http://positionabsolute.net/blog/2007/04/ajax-request-queue.php



On Nov 24, 8:30 am, "Alex McAuley" <webmas...@thecarmarketplace.com>
wrote:

> Yes...
>
> Objects and thier properties are built and stored in memory (how else would
> they get built) - the CPU does the calculations and outputs the opcode to
> the browser (which reads from memory) what it needs to do with the object
> (In very simple terms)... So it stands to reason that if you dont remove the
> Object from memory it will just add to the memory bracket.
>
> To test...
>
> Build a test page with a periodical ajax request and (on winblows) watch the
> RAM that for instance firefox uses in the task manager go up and up and up.
>
> Then close the whole browser (so it starts clean again) and assign the
> periodical updater to a variable
>
> var request=new Ajax.Periodical...({});
>
> request=null;
>
> And watch the difference between what happend in the first test and the
> second...
>
> In the second test the browser frees up 60-80% of the memory that it used to
> make/process the request by nulling the object back to a null byte
>
> If you look on TJ's proto scripty wikidot my results are there and the code
> that accompanies it.
>
> I assumed it was common knowledge that people garbage collected ajax
> requests... Its not just prototypejs but every ajax style library that does
> not garbage collect these requests
>

> ...
>
> read more »

[Eric]

>And next, because an array is much more flexible than variables. you

I am sorry David, but I don't agree with you on this :o)

An object variable is ways more flexible than an array. Especially if
you add some methods to its prototype to fit your needs.

And it is probably overkill in this case, where an incremented int
would do it unless you actually need the result objects of every
previous requests (which is not the same thing than "need to be
executed after every previous requests" which is the need expressed by
maalek).

Alex: That's weird, but I was thinking the xhr object was stored in
the closure of the Ajax.Request object, and garbage collected after
the last callback was called (unless you store a reference to this
object in another variable of course).
It seems I am obviously wrong here.... I guess I'll have to have a
look in the source again :o)

>var request=new Ajax.Periodical...({});
>
>request=null;

If you nullify the Periodical thingy, will it continue to be called?

[Alex McAuley]

I'll dig out the testbed that i made for it as it was a long time ago now
that i did it and i cant remeber if i wrapped it in a periodicalupdater or
an AjaxPeriodicalUpdater...

Alex Mcauley

http://www.thevacancymarket.com
----- Original Message -----
From: "Eric" <lefa...@gmail.com>
To: "Prototype & script.aculo.us" <prototype-s...@googlegroups.com>
Sent: Friday, November 27, 2009 3:48 PM
Subject: [Proto-Scripty] Re: Sychronize many asynchronous Ajax.Request

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